Superbasic alkaline earth metal sulfonates



SUPERBASIC ALKALINE EARTH METAL SULFONATES Raymond C. Schlicht, Wappingers Falls, N. Y., assignor No Drawing. Application July 20, 1956 Serial No. 598,088

7 Claims. (Cl. 252-33) This invention relates to improved oil soluble superbasic alkaline earth metal sulfonates and method of preparing same.

Oil-soluble superbasic sulfonates contain higher quantities of alkaline earth metal than is present in the corresponding normal sulfonate salts. Therefore they are in demand where high concentrations of alkaline earth metal are desired in oleaginous vehicles such as in lubricant compositions. The key to forming such superbasic material is the use of a promoter in the reaction mixture as is exemplified by a number of prior U. S. patents, for example: 2,616,911 and 2,616,924. The promoted products shown in these patents are characteristic superbasic sulfonates.

At the present time superbasic sulfonates are broadly characterized as complexes, and the precise molecular structure of these products is not generally known. It has been postulated that these high metal content complexes are actually colloidal suspensions or dispersions of metal compounds peptized by the normal salt of the sulfonic acid in such complex.

Heretofore, the most common promoter used has been an alkylated phenol such as nonyl phenol. Other classic promoters disclosed for formation of the superbasic sulfonates have been lower molecular weight aromatic carboxylic acids, lower molecular weight sulfonic acids, cresols, xylenols, catechol, beta-naphthol, and a host of other compounds all of which can be typified as being acidic in character.

In a typical preparation of superbasic sulfonates one mixes an oil-soluble hydrocarbyl sulfonic acid and/or normal alkaline earth metal salt thereof, a basicallyreacting alkaline earth metal compound such as the hydroxide, oxide, carbonate, bicarbonate, sulfide, hydrosulfide, hydride, basic carbonate, or the like in amount sufiicient to establish a metal ratio in excess of one, a non-acidic vehicle for the basically-reacting alkaline earth metal compound, e. g., water, a lower alkanol or a lower alkanediol, and the promoter substance; heats the mixture to drive off substantially all the hydroxy vehicle and incidental water of neutralization; and stabilizes the resulting product by neutralizing excess alkalinity, usually by blowing with an acid anhydride gas such as carbon dioxide. Excess solids in the mixture can be filtered oflf prior to or after the neutralizing treatment. The resulting product can be incorporated into mineral lubricating oil, greases, cutting oils and a variety of other oleaginous vehicles. Metal ratio as used herein is defined as the ratio of total amount of alkaline earth metal in the mixture to the amount of alkaline earth metal theoretically combinable as a normal salt with the kind of sulfonic acid present.

I have now discovered that improved superbasic hydrocarbyl sulfonates can be made by using, instead of a phenol, or a carboxylic acid, or a lower molecular weight sulfonic acid, or similar promoter substance acidic in nature, at least one dibenzo heterocyclic imine, i. e., caratent naphthene sulfonic acids, and monolCe bazole, phenothiazine, phenoxazine, alkylated derivatives thereof, as the promoter substance. Such promoters are organic bases and will form salts with. strong mineral acids such as hydrochloric.

Ordinarily in the practice of my process I use 0.1 to 0.5 gram mol of the imine per equivalent of sulfonic acid (i. e., per mol of monobasic sulfonic acid, per half mol of alkaline earth metal sulfonate, or per half mol, of disulfonic acid, etc.), and for efliciency and economy in the practice of my process I prefer to use about 0.25 mol of the imine per equivalent of sulfonic acid. For efficiency and economy in the practice of my process I prefer to use phenothiazine or an alkylated phenothiazine as the promoter. Suitable nuclear carbon monoand polyalkylated phenothiazines can be made, for example, by the method of Canquil et al., Comptes Rendus, 236, at pages 363-5. While the alkyl snbstituent or substituents assist in blending the promoter with many kinds of hydrocarbon oils, lower alkyl groups of not more than 4 carbon atoms are quite adequate for such purpose.

The basically-reacting alkaline earth metal compounds useful in my synthesis are those of barium, strontium, calcium and magnesium. The most effective and also desirable from a standpoint of ease of manufacture is a basically-reacting barium compound, e. g., barium hydroxide, barium hydroxide octahydrate, barium oxide or the like. The basically-reacting alkaline earth compound is dissolved or slurried in one or more non-acidic hydroxy vehicles which can be water, a lower alkanol of l to 3 carbon atoms, a lower alkanediol of 1 to 3 carbon atoms, or the like. I have found methanol the superior one of such vehicles for my preparation, and, accordingly, I prefer to use it. Generallyabout 2 to 20 mols of vehicle are used per equivalent weight of alkaline earth metal and nuclear carbon in the reaction mixture.

The hydrocarbyl sulfonic acid compound useful in my process can be the oil-solublehydrocarbyl sulfonic acid itself and/or an alkaline earth metal salt thereof, and is preferably the sulfonic acid for efficiency and economy. In the case where an alkaline earth sulfonateis used as a starting material, it is of course advantageous to use a basically-reacting compound of the same alkaline earth metal in the preparation. Typical oil-soluble hydrocarbyl sulfonic acids for superbasing are the mahogany sulfonic acids, petrolatum sulfonic acids, monoand polywax substituted benzene sulfonic acids, monoand polywax substituted naphthalene sulfonic acids, paraffin wax sulfonic acids, polyisobutylene sulfonic acids, petroleum and poly-wax substituted cyclohexyl sulfonic acids.

The preparation of the superbasic sulfonate of my invention comprises: mixing the oil-soluble hydrocarbyl sulfonic acid (and/or alkaline earth metal salt thereof), sufiicient of the basically-reacting alkaline earth metal compound to establish a metal ratio in excess of 1 and preferably in excess of 2 (generally 3 to 4) in the mixture, the hydroxy vehicle, and the imine promoter; stripping oif substantially all said hydroxy vehicle and any incidental Water of neutralization; and neutralizing residual alkalinity in the resulting mixture. The stripping of vehicle and water can be done at superatmospheric or subatmospheric pressures and with or without a flow of inert stripping gas and/or mechanical agitation, but for efiiciency and economy when using the preferred lighter hydroxy vehicles such as methanol, l prefer to use simple heating at substantially atmospheric pressure for this step. The maximum temperature of such stripping operation can be broadly from 200 to 450 F. for the hydroxy vehicles generally and, with the preferred vehicles, is about 250 to 300 F.; the time of heating at the maximum temperature to remove practically all free hydroxy 2" u? vehicle andwater of'neutralization can be from about to'ab0ut'8h0urs, and is usually 1 to 3 hours.

Neutralization of residual alkalinity is done preferably by blowing with carbon dioxide, e. g., substantially pure carbon dioxide, air. containing carbon. dioxide, flue. gas containing carbon dioxide, or the like. Alternatively or concurrentlylcan also use other. acidic anhydride gases such as S S0 HCl, N0 H 8, CS COS, PCl SOCl C etc., or dilute mineral acids, e.. g., sulfuric, nitric, hydrochloric, or organic acids suchas acetic, stearic, and thelike. Advantageously the neutralization is conducted before cooling and filterirng the mixture which has been stripped offhydroxy vehicle. Itis advisable to neutralize at a temperature above 100 C..to obtain desirably rapid reaction rate. andto maintain the product substantially free. of water. Ordinarily it takes /2 to 3 hours of CO blowing tov obtainsubstantial' neutrality, ,i. e. a neutralization number ofthe reactionmixturefrom 0 to aboutf8 (alkaline). Filtrationlis best done subsequent to neutrali'zationon a cold mixture thinned with a low boiling hydrocarbon. solvent such as pentane, methyl pentane, heptane or the like usinga diatomaceous silica or other filtering assistants. After filtration the solvent can be stripped ofi in conventional manner.

A typical lubricating composition made with my novel additive comprises80 to 99.5 weight percent of mineral. lubricating oil and 0.5 to 10 weight percent of my superbasic alkaline earth metal sulfonate. Optionally the lubricating oil can contain small amounts of other additives such as sulfurized sperm oil, zinc dialkyldithiophosphate, and viscosity index improvers such as sulfurized polyisobutylene,.and the like, but need not contain such other additives to be superior to the base mineral oil itself. The outstanding performance of a lubricating oil compounded with a superbasic sulfonate made according to invention principles using phenothiazine as promoter substance is shown by the results of the MacCoull corrosion test run on lubricating oil compositions hereinafter described. (The MacCoull corrosion test measures bearing weight loss under controlled conditions and is described in the magazine Lubrication, volume 27, page 1-07, September 1941, published by The Texas Company, New York, N. Y.) The tests were run at 350 F. using copper-lead bearings.

These lubricating oil compositions were made by blending a phenothiazine-promoted supcrbasic barium sul fonate, zincdialkyl dithiophosphate sold under the tradename.LZ.-677 by the Lubrizol Corporation, and a high. grade. SAE weight mineral lubricating oil base; cornpositionA, below, contained 3.0 weight percent of the superbasic sulfonate, 0.5 weight percent of the zinc dialkyl dithiophosphate and 96.5 weight percent mineral lubricating oil; composition B contained 3.0 weight percent of the superbasic sulfonate, 0.2 weight percent of the zinc dialkyl dithiophosphate, and 96.7 weight percent of themineral lubricating oil.

Average bearing weight loss, mg.

Time

2 Hours 10 Hours Neutralization N (S) at 10 Hours 0.

Average bearing weight loss, Mg. 2 hours 0 4 hours 0 6 hours 0 8 hours L 3 10 hours 62 Neutralization No. (S) at 10 hours 6.4

The phenothiaZine-promoted superbasic alkaline earth metal sulfonate used in the above tests was made in the following manner: a slurry of anhydrous barium hydroxide in methanol vehicle was mixed with a blend of the promoter in oil-thinned petroleum sulfonic acids having average mol weight of 450 (oil-free basis), the particular sulfonic acids being sold by L. Sonneborne & Sons, Inc, under the trade-name Petronic Acid. The sulfonic acid had previously been diluted with 0.5 part of a naphthene base oil, having API gravity of 19 to 22 and viscosity of 300 to 324 SSU at 15., per part of sulfonic acid. The quantity of promoter used was 0.25 mol per equivalent (mol) of the sulfonic acids. The proportion of barium hydroxide to sulfonic acid used was 1.75 mols per mol of sulfonic acid, this establishing a metal ratio of 3.75 in the mixture; the mixture was heated up to C. and maintained there for about 2 /2 hours, thereby stripping out practically all of the methanol and water of neutralization in the mixture. The vapor space in the reaction vessel was blanketed with nitrogen to assist in stripping. Neutralization was obtained by blowing the mixture with carbon dioxide. The novel superbased product was thinned with methylpentane, filtered with the assistance of a diatomaceous silica (sold underthe-trade-name of Super-Col by the lohns-Manville Sales Corporation) and the methylpen tane stripped off. The analytical results of the preparation are given below:

Wt. percent barium in product Metal ratio in product Wt. percent barium in product 12.9. Metal ratio in product; 2.10

The product was completely dispcrsable in mineral oil.

Obviously, many modifications and variations of the invention, as hereinbeforc set forth, may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

I claim:

1. In a process for preparing superbasic alkaline earth metal sulfonates by heating a mixture containing at least one compound selected from the group consisting of. oilsol'uble hydrocarbyl sulfonic acids and alkaline earth metal salts thereof, a basically-reacting alkaline earth metal compound, and a promoter substance and neutraliz: ing residual alkalinity in the heated mixture with an acidic anhydride gas, the improvementwhich comprises using as the specific promoter substance 0.1 to 0.5 gram mol of at least one dibenzo heterocyclic imine per equivalent of sulfonic acid in said mixture.

2. The'process of claim 1 wherein said imine is phenothiazine.

3. The process of claim 1 wherein said imine is'carbazole.

4. The process of claim 1 wherein said basically-reach ing alkaline earth metal compound is a barium com! pound.

5. In a process for preparing superbasic alkaline earth metal sulfonates by adding a basically-reacting alkaline earth metal compound to a mixture of an oil-soluble hydrocarbyl sulfonic acid and a promoter substance to form a reaction mixture, thereafter heating said reaction 5 7. The process of claim 5 wherein the basicallyreacting alkaline earth metal compound is barium hydroxide, the acidic anhydride gas is carbon dioxide and the dibenzo heterocyclic imine is carbazole,

References Cited in the file of this patent UNITED STATES PATENTS 2,451,549 Gzemski Oct. 19, 1948 2,595,140 Heinrich Apr. 29, 1952 2,692,858 Evans et al. Oct. 26, 1954 2,723,236 Assetf et al Nov. 8, 1955 2,727,861 Brown et al. Dec. 20, 1955 2,760,970 Le Suer Aug. 28, 1956 2,781,318 Cyphers Feb. 12, 1957 

1. IN A PROCESS FOR PREPARING SUPERBASIC ALKALINE EARTH METAL SULFONATES BY HEATING A MIXTURE CONTAINING AT LEAST ONE COMPOUND SELECTED FROM THE GROUP CONSISTING OF OILSOLUBLE HYDROCARBYL SULFONIC ACIDS AND ALKALINE EARTH METAL SALTS THEREOF, A BASICALLY-REACTING ALKALINE EARTH METAL COMPOUND, AND A PROMOTER SUBSTANCE AND NEUTRALIZING RESIDUAL ALKALINITY IN THE HEATED MIXTURE WITH AN ACIDIC ANHYDRIDE GAS, THE IMPROVEMENT WHICH COMPRISES USING AS THE SPECIFIC PROMOTER SUBSTANCE 0.1 TO 0.5 GRAM MOL OF AT LEAST ONE DIBENZO HETEROCYCLIC IMINE PER EQUIVALENT OF SULFONIC ACID IN SAID MIXTURE. 